Washable underpad and method for producing an underpad of this type

ABSTRACT

The invention relates to a multilayer washable material which comprises at least one layer of a textile material, the layers being joined to one another using an adhesive composition, which is characterized in that in the interfacial region between each pair of layers bearing against one another there is an adhesive composition in the form of a pattern, and no finishing of the multilayer material, as such and/or of a smaller part obtained therefrom, is carried out. One example of a multilayer washable material of this type is a washable underpad comprising a moisture-permeable top layer material ( 2 ); a moisture-impermeable bottom layer material ( 3 ) and a moisture-absorption element ( 1 ) positioned between them, the top layer material ( 2 ), the bottom layer material ( 3 ) and the moisture-absorption element ( 1 ) being joined to one another. The adhesive composition used is preferably a moisture-curing reactive polyurethane hotmelt material.

BENEFIT CLAIMS

This application is a US National Stage of International Application No.PCT/NL2004/00221 filed 2 Apr. 2004, which claims the benefit of NL1023144, filed 10 Apr. 2003.

The invention relates firstly to a multilayer washable material whichcomprises at least one layer of a textile material and in which thelayers are joined to one another by means of an adhesive composition.

A material of this type is known from US2001/0001300.

The said US application describes a washable textile item and a methodfor producing it in which layers of textile material are joined to oneanother by means of a simulated stitching pattern which is formed from acurable hotmelt adhesive which is applied in the molten form. The layersare placed against one another and the adhesive penetrates into thefibre structure of the layers as a result of the application ofpressure, so that after curing of the adhesive the layers are joined toone another.

A known material of this type has the drawback that the way in which thevarious layers are joined adopts a stitching pattern character, with theresult that wrinkles may occur during use. If a multilayer material ofthis type is used, for example, as a washable incontinence underpad, thepatient may find wrinkles of this nature very unpleasant and evenpainful and/or harmful.

It is an object of the present invention to provide an improved washablemultilayer material of the abovementioned type in which at leastwrinkling can no longer occur, and to this end is characterized in thatin the interfacial region between each pair of layers bearing againstone another there is an adhesive composition in the form of a patternwhich prevents wrinkling, and no finishing of the multilayer material,as such and/or of a smaller part obtained therefrom, is carried out.

The term in the form of a pattern which prevents wrinkling in thiscontext is to be understood as meaning a pattern shape which on the onehand has a density of joining locations between the layers which is suchthat wrinkling can only occur at a micro-level and is not considered aproblem by the user, yet on the other hand, the total bonded area issufficiently small for the multilayer material to be extremely flexiblein use. The following text will explain examples of such patterns.

Where the above text refers to finishing, this will often be understoodas meaning edge finishing. However, it should be emphasized that thestitching work which is known from the prior art and is used to fix thevarious layers with respect to one another is also eliminated.Therefore, the elimination of finishing is to be understood in a broadsense; the only work which is carried out if required in order to obtaina multilayer, ready-to-use material of the desired format is a cutting,trimming or stamping operation. As an example of a multilayer washablematerial according to the invention, it is possible to think of underpadmaterial as mentioned above; mention may also be made of bandages,wound-covering material, stoma attachment material, dressing material,pantyliners, sanitary towels and many others. The multilayer washablematerial is expediently a material comprising three layers, in whichcase, by way of example, an absorption body is surrounded by coveringlayers selected from moisture-permeable and moisture-impermeablematerial. If one of the layers is to be moisture-impermeable, thismaterial may, for example, be a moisture-impermeable plastic material,such as polyurethane, polyethylene and the like.

Another multilayer material may, for example, comprise three layers withthe top layer material and bottom layer material being identical. Amaterial of this type can be used on both sides, making it very easy touse for the user.

The washable material, on account of the way in which the layers havebeen joined in a pattern shape, is sufficiently cohesive to allow it tobe used as such without any finishing after it has been cut or trimmedinto any desired pattern and to allow it to be reused, after washing,without any significant fraying or loss of cohesion occurring over thecourse of time.

As has already been indicated, the pattern shape which preventswrinkling may be in a wide range of forms, and is expediently selectedfrom:

-   a) a dot lining pattern,-   b) separately positioned pattern parts which are separated by    regions where there is no adhesive composition,-   c) a number of pattern parts which are identical in shape and one or    more pattern parts of a different shape,-   d) the patterns described under b) and/or c), with one or more    pattern parts being formed from a dot lining pattern,-   e) a dot lining pattern as described under a) in which there are    parts without any dots,

and combinations of the patterns described under a) to e).

The number of possible pattern shapes that can be used is not limited tothose indicated above; many other options will be obvious to the personskilled in the art on reading the present description. Any pattern whichis sufficiently dense to prevent wrinkling and at the same time issufficiently open (i.e. has a sufficient surface area without anyadhesive) to prevent the material from becoming inflexible is suitablefor use in the present materials.

In particular, the invention relates to a washable underpad comprising amoisture-permeable top layer material; a moisture-impermeable bottomlayer material and a moisture-absorption element positioned betweenthem, the top layer material, the bottom layer material and themoisture-absorption element being joined to one another.

In the context of the present invention, the term underpad is to beunderstood as meaning on the one hand a ready-to-use underpad as suchwhich can be used directly to provide comfort to a bedridden incontinentpatient and to protect the mattress on which the patient is lying.

On the other hand, the underpad may also be a material from which it ispossible to make one or more underpads or other objects in which thefunction of the material is of benefit.

Whereas the prior art often required joining by stitching or the like inorder to join the various layers to one another in such a manner thatthere was no separation of the layers during washing of the underpad,the Applicant has now discovered that by using adhesives it is possibleto join the top layer material and the bottom layer material to themoisture-absorption element in such a manner that the underpad has anexcellent long-term washability without separation of the layersoccurring. By suitably selecting the pattern shape of the adhesivecomposition, it is possible to effectively prevent wrinkling in theplane of the underpad.

The moisture-permeable top layer material for an underpad can beselected from numerous materials which have a good moisture-permeabilityand are substantially hydrophobic. The top layer material is, forexample, expediently a knitted material which comprises fibres selectedfrom polyester, polyamide and polyethylene or mixtures thereof. It isalso possible to use mixtures of synthetic and natural fibres, such aspolyester/cotton, for example in a ratio from 80% polyester/20% cottonto 50% polyester/50% cotton.

In certain cases, if the absorption element has an extremely highabsorption capacity, the top layer material may even be made from 100%cotton. In particular, a suitable top layer material is a knittedpolyester material which is raised on the side which comes into contactwith the patient, so that a soft surface is obtained. It is alsopossible to use a towelling layer or a dryness layer, in particular ifthe underpad is provided with a non-fraying edge, as explained below.

A moisture-absorption element which can be used in the washable underpadaccording to the invention is expediently an assembly of chemicalfibres, such as viscose or modified viscose and synthetic fibresselected from polyester, polyamide, polyacrylate, polypropylene and thelike; a moisture-absorption element of this type is described in theApplicant's

The term “chemical fibres” relates to a fibre which is based on anatural product, such as cellulose, and which has been converted into aform which is suitable for human use by means of a chemical treatment. Asynthetic fibre is a fibre produced from a polymer which is producedentirely by chemical synthesis without any natural product base beingpresent.

The moisture-absorption element expediently comprises, for example, 90to 10% chemical fibres, such as viscose or modified viscose, and 10 to90% synthetic fibres, such as polyester, polyamide, polyacrylate,polypropylene and the like.

The moisture-absorption element expediently comprises 10 to 40% chemicalfibres and 90 to 60% synthetic fibres, and the moisture-absorptionelement is preferably composed of 70% polyester and 30% viscose, morepreferably 85% polyester and 15% viscose, with needling having beencarried out in order to obtain optimum bonding between the fibres. Theneedling of the fibre mixture results in a cohesion which is such thatthe moisture-absorption element can withstand numerous washes withoutproblems.

If desired, the moisture-absorption element may, in order to accelerateits drying after it has been washed, comprise perforations which extendover at least part of the height of the moisture-absorption element. Itis expedient for the perforations to extend over the entire height ofthe moisture-absorption element. The perforations generally have adiameter of from 1 to 5 mm and a centre-to-centre distance of from 8 to30 mm. In particular, the perforations have a diameter of approximately3 mm and a centre-to-centre distance of approximately 12 mm.

In the absorption element, the chemical fibres, such as viscose ormodified viscose generally have a thickness of from 1 to 8 dTex and alength of from 30 to 100 mm, while the synthetic fibres, such aspolyester, comprise fibres with a thickness of from 1 to 10 dTex and alength of from 30 to 100 mm. The synthetic fibres, such as polyester,may expediently comprise additional polyester with a thickness of lessthan 1 dTex and a length of from 30 to 80 mm.

It is expedient to use a mixture of chemical fibres and synthetic fibresin the moisture-absorption element, as has been explained above.However, it has been found that moisture-absorption elements whichconsist entirely of synthetic fibres can also be used with success.Tests using moisture-absorption elements consisting entirely ofpolyester fibres were very successful. Advantages obtained included,inter alia, mechanical stability, washability (no residual soiling onaccount of the absence of absorption in the fibre), hygiene, bonding tothe adhesive compositions.

The moisture-impermeable bottom layer material may be any suitableplastic material, such as polyvinyl chloride, polyethylene, polyurethaneand any other synthetic, moisture-impermeable material. The material maybe thermoplastic or non-thermoplastic and must not, of course, have anyadverse effect on the skin of the patient using it.

The bottom layer material may be a textile material which is coated witha plastic material.

It is also possible for a textile material to be coated with a plasticfilm, such as PVC or PU by laminating or adhesive bonding and then to beused as the bottom layer material.

In a highly attractive embodiment, the bottom layer material maycomprise a non-slip layer in the form of a coating in pattern form onthe side which faces away from the absorption body. The pattern shapemay comprise any of the shapes described above, but is expediently a dotpattern. A non-slip pattern of this type prevents, for example, anunderpad from slipping with respect to the mattress on which it rests.Suitable materials for a dot pattern of this type include theconventional rubber-like plastic materials, such as PU, PVC andsynthetic rubber; the dot pattern is expediently formed by printing thebottom layer material using screen printing followed by drying/curing ofthe dot coating layer which has been applied.

In general, of course, the materials should be selected such thatbonding is produced between the various layers of the washablemultilayer material with the aid of the adhesives used in the invention.

It is expedient for the adhesive used in each of the interfacial regionsreferred to above to be employed in a pattern shape. Obviously, itshould be ensured that moisture can pass freely from the top layermaterial to the moisture-absorption element, and it is therefore highlyimportant that there should be regions where adhesive is presentalternating with regions where no adhesive is present, in order to allowunimpeded passage of moisture.

In one attractive embodiment, the adhesive is present in the form of adot lining pattern. In this case, the dot lining pattern extends overthe entire surface of the washable underpad; the pattern is selected insuch a manner that there is sufficient free space between the dots ofadhesive not to impede passage of moisture.

In a highly attractive embodiment, the pattern of adhesive is composedof separate pattern parts which are separated by regions where there isno adhesive. Of course, a very wide range of types of pattern may beused, but it is advantageous for there to be a number of pattern partswhich are identical in shape together with one or more pattern parts ofa different shape.

In a highly advantageous embodiment, a pattern part of a different shapeis a rectangular border, the external dimensions of which correspond tothe dimensions of the washable underpad. The rectangular border, whichis therefore present in the interfacial region between top layermaterial and moisture-absorption element and in the interfacial regionbetween moisture-impermeable bottom layer material and the absorptionelement, ensures excellent bonding in the border region of the underpad,while inside the rectangular border there may be carefully selecteddifferent pattern parts which are responsible for bonding between thethree layers in that region.

When selecting the shape of the other pattern parts, it is importantthat the pattern parts be selected in such a manner that no wrinklingoccurs in the underpad, which can give rise to skin problems for thepatient/user. The pattern parts may, for example, be circles with adiameter of between 3 and 50 mm; pattern parts with a diameter of 5 mmhave given good results. The centre-to-centre distance of the patternparts may be from 10 to 100 mm, preferably 10 to 60 mm, more preferably10 to 25 mm. In addition to circles, it is, of course, also possible touse other shapes of pattern parts in the region inside the rectangle,such as for example a spiral structure.

If in particular the top layer material is selected appropriately, in ahighly advantageous embodiment there is no need for a finishing edge. Inparticular if the top layer material is a knitted fabric, in whichspecial measures are taken to prevent fraying, there is no need to applya separate finishing edge.

In one attractive embodiment, each of the pattern parts is composed of acollection of separate dots. As has been stated above, it is importantto ensure unimpeded passage of moisture from the top layer material tothe absorption element; forming any pattern parts from dots prevents thepassage of moisture from the top layer material to the absorptionelement from being impeded.

Numerous types of adhesives can be used in the underpad as describedabove. Firstly, mention may be made of crosslinking adhesives whichafter application cure over the course of a certain time, if appropriatewith heat being supplied.

Examples which may be mentioned include epoxy resin/hardenercompositions; polyester resin/hardener compositions and moisture-curablepolyurethane or cyanoacrylate compositions.

It is also possible to use thermoplastics which are applied to onematerial in the molten state, with the material then being brought intocontact with another material before the thermoplastic has set as aresult of cooling, and with the assembly formed then being allowed tocool until the thermoplastic sets. This process is repeated for theaddition of further layers.

Suitable thermoplastics include polyvinyl chloride, polyethylene,polypropylene, polyurethane and the like.

It is also possible to use ethylene vinyl acetate; copolyamide,copolyester.

Examples of suitable thermoplastics which may be mentioned includecopolyester No. 1655 produced by EMS-Chemie with a melting point of 188°C. and Unex 1426 produced by Dakota, with a melting point of 140° C.

The Applicant has carried out extensive research into adhesives whichcan be used, and it has been found that excellent results in terms ofthe durability of the bonding during washing, during treatment in anautoclave and over the course of time are obtained if the adhesive isselected from a fully moisture-cured reactive hotmelt adhesive, such asa fully moisture-cured reactive polyurethane hotmelt adhesive and afully moisture-cured reactive polyalkene hotmelt adhesive. Reactivehotmelt adhesives of this type are known, and of these the fullymoisture-cured reactive polyurethane hotmelt adhesive is preferred.

A polyurethane hotmelt adhesive which reacts with moisture is formed byreaction of (HO-polyol-OH)_(x)+(OCN..NCO)_(y)→OCN-urethane-NCO, where yis greater than x. The reactive urethane formed in this way is athermoplastic material which, when used in air, can be fully cured bywater from the air to form a crosslinked polyurethane which is a setmaterial. Full curing can be effected using moisture from the air; ofcourse, it is also possible for full curing to be effected by deliberateaddition of water to the reactive thermoplastic urethane material, orwater can be supplied, for example, by blowing steam onto the adhesivematerial. The reactive materials can be obtained from a wide range ofsources. Mention may be made, for example, of HPUX9717 from Forbo SwiftAdhesives SA of Blois, France and JOWATHERM 603.78 produced by JOWATKLEBSTOFFE of Detmold, Germany, both products which are examples ofreactive polyurethane hotmelt adhesives.

HPUX9717 from Forbo Swift can be applied at a temperature of from 100 to120° C.; the product is workable in air for from 1 to 5 min and evenafter 30 s has attained a green strength which allows it to be handled.The curing time is 24 h at a relative humidity of 75%.

JOWATHERM Reaktant 603.78 has a processing temperature of approximately140° C. and a reaction time of approximately three days, depending onthe ambient conditions.

Other suitable types of material include HPUX 9833 and HPUX 9946produced by Forbo Swift.

Further suitable JOWATHERM grades include 603.00; 603.01; 603.07; 603.08and 603.09.

In the text which follows, the multilayer washable material is alwaysassumed to be composed of three layers, namely a moisture-permeable toplayer material, a moisture-absorption element and a moisture-impermeablebottom layer material.

For certain applications, it may be expedient for additional layers tobe present in addition to the said three layers and for the washableunderpad as described above also to comprise one or more additionallayers of material selected from an anti-allergy layer, a resilient foamlayer, a dispersion layer, a bedsore-inhibiting layer and an anti-odourlayer, which are bonded to the absorption element and the top layermaterial or the bottom layer material. Depending on the patient, it ispossible, by selecting the additional layer or layers of material, toprovide optimum comfort for the patient while he is bedridden.

The invention also relates to a method for producing amultilayer-washable material which comprises at least one layer of atextile material, at least comprising a top layer material, a bottomlayer material and an interlayer material positioned between them,wherein a top layer material, a bottom layer material and an interlayermaterial are provided and are joined to one another using an adhesivecomposition, which is characterized in that an adhesive composition isapplied in the form of a pattern which prevents wrinkling both in theinterfacial region which is to be formed between top layer material andinterlayer material and in the interfacial region which is to be formedbetween bottom layer material and interlayer material, and the layersare brought to bear against one another and are joined to one another asthe adhesive composition sets, with no finishing of the multilayermaterial as such and/or a smaller part which is cut from it, beingcarried out.

Attractive embodiments of the above method are described in dependentclaims 9-14, which will be explained in more detail in the text whichfollows.

Depending on the type of method which is carried out, the layers ofmaterial to be used in the method may be in sheet or web form. The sheetform is generally used in discontinuous processes, whereas the web formis preferred for continuous processes.

In one particular embodiment, the method according to the inventionrelates to the production of a washable underpad at least comprising amoisture-permeable top layer material, a moisture-impermeable bottomlayer material and a moisture-absorption element positioned betweenthem, wherein a moisture-permeable top layer material, amoisture-impermeable bottom layer material and a moisture-absorptionelement are provided and are joined to one another.

According to the invention, an adhesive composition is applied both inthe interfacial region which is to be formed between top layer materialand moisture-absorption element and in the interfacial region which isto be formed between bottom layer material and moisture-absorptionelement, after which the layers are brought to bear against one anotherand are joined to one another.

The adhesive composition can be applied in various ways, among whichspraying, lamination, application using a slot coater and printing maybe mentioned as attractive embodiments. In the case of lamination,consideration may be given to a layer of adhesive which is incorporatedbetween two layers of release material; removing one of the layers ofrelease material makes it possible for the adhesive material to be stuckto one layer selected from the top layer material and the bottom layermaterial; removing the second layer of release material enables the toplayer material or bottom layer material which has been provided withadhesive in this way to be stuck to the moisture-absorption element.This operation is repeated in order to form the washable underpadcomprising three layers.

In the case of application by printing, mentioned may be made ofintaglio printing and screen printing, although the invention is notrestricted to these two specific methods. In the case of intaglioprinting, adhesive is applied with the aid of a roller which includesindentations, with applications of up to 25 g/m² being readily possiblein general.

Higher levels of application can be realized by screen printing, inflat-bed or rotary form.

If the adhesive composition is sprayed, the adhesive composition isgenerally applied to the top layer material and the bottom layermaterial, after which the said layers are joined to themoisture-absorption element under pressure. The adhesive composition tobe used in the method according to the invention is selected from anonreactive thermoplastic material which is solid under ambientconditions and a moisture-curable plastic material, while it is appliedin the form of a melt at a temperature higher than the melting point ofthe plastic material used.

The adhesive composition is expediently a moisture-curing plasticmaterial, while the application takes place in the form of a melt at atemperature which is higher than the melting point of the plasticmaterial used.

Obviously, the moisture-curing plastic material requires a certain timeafter application to the various layers and after they have been finallystuck to one another before it is fully cured. During the curing period,the contact between the various layers will be maintained in order toensure final bonding which is able to withstand handling duringsubsequent use and washing.

In one attractive embodiment of the method, the moisture-curing plasticmaterial is applied to the top layer material and the bottom layermaterial. Both the top layer material and the bottom layer material arerelatively dense materials which are eminently suitable for receiving amoisture-curing plastic material without loss of significant propertiesof moisture-curing plastic material occurring as a result ofbreakthroughs.

Of course, if desired the moisture-curing plastic material can also beapplied to both sides of the moisture-absorption element; it should thenbe ensured, by selection of the application technique, that penetrationof the plastic material remains limited to the surface layers on bothsides of the moisture-absorption element.

Application of the molten moisture-curing plastic material by printingcan be executed in various ways; mention may be made of intaglioprinting and screen printing.

In one attractive embodiment, the molten moisture-curing plasticmaterial is applied with the aid of screen printing, in which case atleast the screen-printing stencil used is heated to above the meltingpoint of the moisture-curing plastic used.

Obviously, in addition to the screen-printing stencil which is heated toabove the melting point of the moisture-curing plastic used, it is alsopossible for the moisture-curing plastic material itself and/or thesqueegee used to be heated in order to ensure that there is no prematuresolidification of the moisture-curing plastic material in the stencil.

Screen printing can be carried out in various ways.

With flat-bed screen printing, in which the stencil is a flat frame witha (metal) gauze tensioned inside it, it is possible to provide web-likematerials with a printed pattern; it is also possible for separate partsof the material (for example of the size of the washable underpad) to beprinted with a pattern of adhesive composition. It is also possible forrotary screen printing to be used in an extremely attractive embodimentof the method according to the invention, in which case it is possibleto employ one or more seamless cylindrical metal stencils. In rotaryscreen printing, a seamless, cylindrical metal stencil is brought intorotary contact with, for example, an endless belt, with the materialwhich is to be provided with a pattern or is to be printed while itrests on the endless belt by means of the rotating stencil. In thiscase, therefore, the printed pattern comprises a molten moisture-curingplastic material. The rotary screen-printing stencils used may be ofvarious types and structures; Stork Prints of Boxmeer (NL) suppliesstencils of this type, as well as devices in which stencils of this typecan be used. Stencils can be obtained in a wide range of finenesses,thicknesses and diameters; a stencil used in the method described herewas denoted CP52-12-200, where CP52 stands for 52 holes per cm². Theopen percentage of a stencil of this type is 12%, and the wall thicknessof the stencil is 200 μm. Another type of stencil which gave goodresults is CP52-18-200.

The moisture-curing plastic material used is preferably selected from areactive polyurethane hotmelt adhesive and a reactive polyalkene hotmeltadhesive; of these, the reactive polyurethane hotmelt adhesive ispreferred.

As has been described above, a number of materials of this type arecommercially available; good results have been obtained using HPUX9717produced by Forbo Swift of Blois, France and JOWATHERM REAKTANTPUR-Hotmelt 603.78 produced by JOWAT KLEBESTOFFE of Detmold, Germany.

The method in accordance with the embodiment described above usingrotary screen printing can be carried out in various ways.

For example, in a one-head machine, that side of the top layer whichfaces the moisture-absorption element can first of all be provided withan adhesive material, after which the absorption element is laminatedonto it. As the second step, the adhesive material is applied to thatside of the bottom layer material which, in the washable underpad, bearsagainst the other side of the absorption element, after which theassembly formed in the first step is laid against that side of thebottom layer material which has been coated with the adhesive material.Steps one and two are carried out separately and in succession using amachine with one printing station.

In general, to form washable multilayer material, such as for examplematerial for washable underpads, rotary screen printing is used to applya pattern of a moisture-curable plastic material to a moisture-permeabletop layer material and to a moisture-impermeable bottom layer material,and the materials which have been coated in this way are combined with amoisture-absorption element, in such a manner that those sides of thetop layer material and the bottom layer material which contain themoisture-curable plastic material come to bear against the two surfacesof the moisture-absorption element, and curing of the moisture-curableplastic material bonds together the top layer material, bottom layermaterial and moisture-absorption element.

The above text has described the application of the adhesive to the toplayer material and the bottom layer material and the joining of thesematerials to the moisture-absorption element.

Obviously, if desired, it is also possible for the adhesive to beapplied by printing to the two flat sides of the moisture-absorptionelement, after which the moisture-absorption element is brought to bearagainst the top layer material and the bottom layer material in order toform a washable underpad. In this case, the printing of themoisture-absorption element and the combining of this element with thetop layer and bottom layer material can be carried out in a singleoperation; it is also possible to carry out separate operations ofprinting the moisture-absorption element and bringing it to bearagainst, for example, the top layer material and then printing the otherside of the moisture-absorption element and bringing it to bear againstthe bottom layer material.

The general method referred to above can be carried out using both asingle-head rotary screen-printing device and a two-head rotaryscreen-printing device.

However, it is expedient for the top layer material and the bottom layermaterial to be in web form, while moisture-curable plastic material isapplied to both materials simultaneously with the aid of two rotaryscreen-printing stencils, and the top layer and bottom layer materialswhich have been coated in this way are brought to bear against amoisture-absorption element in web form, after which moisture-curing ofthe curable plastic material bonds together the top layer material,bottom layer material and moisture-absorption element.

It is preferable for a method of this type as described above to becarried out continuously, while after an assembly of top layer material,bottom layer material, and moisture-absorption element in web form hasbeen formed, this web is divided by cutting into separate, washableunderpads which, if necessary, are provided with an edge finishing. Inthe continuous embodiment outlined above, the adhesive composition usedwill preferably be a quick-curing adhesive composition, such as amoisture-curing adhesive composition.

Of course, the moisture-curable plastic material as described aboverequires moisture in order to acquire the correct strength through fullcuring. The moisture required can be provided by the atmospherichumidity which is normally present; in areas of low atmospheric humidityand/or during times where the atmospheric humidity is low, it may beadvantageous to accelerate and/or ensure full curing by the applicationof moisture while the method is being carried out.

Therefore, in an advantageous embodiment, to fully cure themoisture-curable plastic material, moisture is supplied in an amountwhich is sufficient to enable the moisture-curable plastic material onthe top layer material and bottom layer material to cure fully. Themoisture used may be liquid, in the form of atomized water; it is alsopossible to use steam.

The latter form is preferred, since this prevents prematuresolidification of the molten moisture-curable plastic material which isthermoplastic during application.

It is preferable for the moisture-curable plastic material to be appliedin pattern form to the top layer material and the bottom layer material.

The pattern shape is selected to be such that wrinkling of the washablemultilayer material, such as a washable underpad, is prevented in use,and is expediently selected from:

-   a) a dot lining pattern,-   b) separately positioned pattern parts which are separated by    regions where there is no adhesive composition,-   c) a number of pattern parts which are identical in shape and one or    more pattern parts of a different shape,-   d) the patterns described under b) and/or c), with one or more    pattern parts being formed from a dot lining pattern,-   e) a dot lining pattern as described under a) in which there are    parts without any dots,

and combinations of the patterns described under a) to e).

A pattern of this type is expediently divided into pattern parts, inwhich case it is advantageous for one pattern part to comprise at leastone rectangle with dimensions which correspond to the dimensions of thefinished washable underpad. In this context, the term rectangle is to beunderstood as meaning a pure geometric rectangle, as well as shapeswhich deviate slightly therefrom. An example of a slightly deviatingshape may have rounded corners or scalloped or slightly rounded sides.In a further attractive embodiment, two sides of the rectangle of therectangular pattern part lie at the edge of the top layer and bottomlayer materials in web form; the other two sides of the rectangle inthis case extend across the width of the top layer and bottom layermaterials in web form.

As has been discussed above, in addition to the rectangle there are alsoparts in pattern form which are located inside this rectangle. As hasbeen stated above, these additional parts in pattern form may adopt allkinds of shapes and densities per unit area; the shape and density aredetermined by the desire to prevent wrinkling in the washable underpadand as far as possible to promote passage of moisture at least from thetop layer material to the absorption element.

Incorporating additional pattern parts inside the rectangle provides theoption of forming air pockets which are distributed over the underpad.These air pockets are of benefit to the patient's comfort and arefavourable to the drying characteristics after washing. One example of ashape of this type is a full-area dot lining, in which, however, roundparts with a diameter of 5 mm and a centre-to-centre distance of 16 mmarranged in an equilateral triangle are left clear of the dot lining. Apattern of this type has proven eminently suitable for the prevention ofwrinkling yet at the same time the material has retained an extremelycomfortable flexibility.

The abovementioned pattern parts, such as the rectangle and additionalpattern parts, are expediently divided into dots.

Obviously, it is also possible for the entire pattern to be composed ofdots and to extend over the entire surface of the top layer material andthe bottom layer material, while otherwise, as stated above, it ispossible for the pattern parts to be composed of dots.

Forming all the pattern parts from dots creates very great flexibilityfor the material of the washable underpad.

Even if the top layer and moisture-absorption element and bottom layerand moisture-absorption element are joined over their entire surface bymeans of dot lining layers, excellent flexibility is obtained, which isto the benefit of the patient's comfort.

During washing, the washable multilayer material, on account of the formof joining by means of the selected pattern and dot structure selected,will undergo controlled shrinkage which does not manifest itself in theform of wrinkling. The materials can shrink automatically, whiledifferences in shrinkage between the layers are absorbed as a result ofthe particular structure and are distributed throughout the entiresurface. After an assembly in web form which is composed of top layermaterial, bottom layer material and moisture-absorption element has beenformed, the assembly formed in this way is divided into washableunderpads, during which process, given an appropriate selection in termsof materials and pattern of adhesive composition, there is no need toapply a separate finishing edge.

Of course, the washable underpad material in web form, after it has beenformed, can also be rolled up and supplied in this form, in which casethe recipient is responsible for cutting and any finishing.

To allow the washable underpad to be matched to the patient'srequirements, it is also possible for one or more additional layers ofmaterial, such as an anti-allergy layer, a resilient foam layer, adispersion layer and a bedsore-inhibiting layer, to be applied, whichlayers are bonded to the moisture-absorption element and the top layermaterial or the bottom layer material. On the other hand, it is alsopossible to add an anti-odour layer, such as a fibre layer whichcontains activated carbon and is assembled in the same way as themoisture-absorption element. The activated carbon may also, optionallylocally, be incorporated in the moisture-absorption element.

The quantity of adhesive composition, for example a moisture-curablepolyurethane hotmelt adhesive as described above, to be applied is from6 to 40 g/m², expediently from 10 to 30 g/m². For an absorption-elementquality of 150 g/m² as standard and 450 g/m² for additional absorptioncapacity, in general a minimum quantity of adhesive composition of 15g/m² will be required. For the application of additional water, ingeneral 3 to 4 ml per m² would be sufficient in order to bring about thereaction; at atmospheric humidity of RH 50% and above, there isgenerally no need to apply water unless it is desired to increase thereaction rate. Extra water should in general be applied if theatmospheric humidity is lower than 50% RH.

The abovementioned weight range for the moisture-absorption elementapplies in particular to multilayer materials of the incontinenceunderpad type. For other applications, different weights will be used:for pantyliner materials 200-800 g/m²; for sanitary towels 50-250 g/m²,etc.

With the abovementioned stencil type CP52-12-200, the open percentage ofthe stencil is approximately 12%; liquefying the adhesive gives asurface coverage of 15%. The openings in the stencil are approximately540 μm; flow produces a curable plastic dot of 604 μm. Thecentre-to-centre distance of the dots is approximately 1540 μm whenusing the abovementioned stencil; the distance between the dots is thenapproximately 936 μm.

The invention will now be explained with reference to the drawing, inwhich:

FIG. 1 diagrammatically depicts a washable underpad;

FIG. 2 shows the structure of a washable underpad of this typeillustrating its individual components;

FIG. 3 diagrammatically depicts a method carried out using a machinewith two heads;

FIG. 4 shows a top layer material which is provided with a pattern of anadhesive composition;

FIGS. 5-10 show various embodiments of the structure and edge finishingof an underpad according to the invention;

FIG. 11 shows an illustration of a screen-printing stencil for applyinga pattern of adhesive composition.

In FIG. 1, a moisture-absorption element is denoted by 1, amoisture-permeable top layer material is denoted by 2 and amoisture-impermeable bottom layer material is denoted by 3. Thematerials 1, 2 and 3 are stuck together with the aid of an adhesivecomposition, such as a moisture-cured, reactive polyurethane hotmeltmaterial. The three layers are of equal size, and by suitable selectionof the pattern of adhesive it was possible to obviate the need for edgefinishing.

FIG. 2 shows the same layers 1, 2 and 3 in a situation in which they arenot yet joined. Dots of an adhesive composition have been applied tothat side of the top layer material 2 which faces the absorption element1; dots of an adhesive composition, which are denoted by 4, have alsobeen applied to that side of the moisture-impermeable bottom layermaterial 3 which faces the absorption element. The dots indicated hereare relatively large dots, which may optionally be subdivided intosmaller dots as discussed above. To complete assembly, the layers 1, 2and 3 are brought to bear against one another and the adhesivecomposition dots are allowed to cure fully, under gentle pressure, sothat the three layers are bonded together.

FIG. 3 shows that a moisture-absorption element 1 is covered on its twosides by a moisture-permeable top layer material 2 and amoisture-impermeable bottom layer material 3, respectively. The toplayer material is coated with adhesive composition 8 with the aid of arotary screen-printing stencil 5 via the intervention of a squeegee 7;to this end, the moisture-permeable top layer material is suppliedcontinuously from a reel (not shown) and is brought to bear against anendless belt 12.

The same operation is carried out on the moisture-impermeable bottomlayer material 3, which is supplied continuously and with the aid of arotary screen-printing stencil 6 is coated with adhesive composition 10in pattern form via the intervention of a squeegee 9. Themoisture-impermeable bottom layer material is supplied and placed ontoan endless belt 11. After the adhesive composition 8 and 10 has beenapplied, the top layer material and the bottom layer material arebrought to bear against the moisture-absorption element using rollers 13and 14, in order to form an assembly comprising top layer material,bottom layer material and moisture-absorption element 15.

The assembly 15 formed in this way is generally rolled up to form areel, after which the material is left to stand for 1 to 5 days in orderto allow the moisture-curable adhesive composition to fully cure.

Obviously, as has been discussed, it is also possible for moisture to beapplied or steam supplied in the area between the rotary screen-printingstencils 5 and 6 and the rollers 13 and 14, in order to promote fullcuring of the adhesive composition or simply to enable the adhesivecomposition to cure fully if the atmospheric humidity is particularlylow.

During the coating of the top layer material 2 and bottom layer material3, the stencil 5, 6 used and possibly also the squeegee 7, 9 and theadhesive composition 8, 10 will expediently be heated, so that theadhesive composition becomes a (viscous) liquid and can be applied tothe materials by printing.

It is generally not necessary to heat the materials 2, 3 and 1, andconsequently the thermal load on these materials is limited to the heatcontent of the adhesive composition applied.

In very exceptional circumstances, it is possible to decide to heat oneor more of the materials 2, 3 or 1; even then, it is possible to limitthe heating to a temperature which keeps the applied hot molten adhesivecomposition in liquid form for sufficient time.

The description given above on the basis of FIG. 3 has assumed that toplayer material 2, bottom layer material 3 and moisture-absorptionelement 1 are of the same width. In one attractive variant, the width ofthe absorption element 1 is less than that of the top layer material 2and the bottom layer material 3, which are of the same width. It is alsopossible for the narrower web of the absorption element 1 to be dividedinto a plurality of webs of even smaller width. The pressure-exertingrollers 13, 14 can be matched to this division in a customary way ordivided into a plurality of rollers over the overall width taking thedivision into account.

The advantage of a multilayer material formed in this way is that itsedges or the edges of the parts formed after division have a thinneredge, facilitating its use. This embodiment also reduces the consumptionof raw materials.

FIG. 4 diagrammatically depicts an adhesive material coating in patternform, in this case on that side of the top layer material which is toface the moisture-absorption element. The pattern comprises arectangular border 21 and deviating pattern parts 22. The pattern parts21 and 22 may be printed over the entire surface; of course, as has beendiscussed earlier, they may also take the form of a dot lining, i.e. thepattern parts 21 and 22 shown can be divided into a large number ofsmall dots which are isolated from one another. Obviously, it is alsopossible for the abovementioned dot lining in turn to be applied inpattern form, i.e. for the dots within the pattern parts 21 and 22 inturn to be arranged in pattern form.

With regard to the stability of the washable multilayer material fromwhich, for example, a washable underpad is formed, in accordance withthe invention having a top layer material, moisture-absorption elementand bottom layer material as described and a moisture-cured plasticmaterial, such as a reactive polyurethane hotmelt (HPUX9717; ForboSwift), it should be noted that the adhesive is able to withstand atreatment for 12 hours in an autoclave (126° C.; 1.45 bar) with 90% ofthe original tensile strength of the polymer being retained. An underpadwhich is formed in the manner described above can withstand from 150 to200 or more washes.

In FIG. 5, the top layer 2 is joined via hotmelt dots to layer 1, whichis narrower, and the assembly of 1 and 2 is joined to themoisture-impermeable layer 3. This produces a finishing, eliminating theneed for fully made-up finishing.

In FIG. 6, top layer 2 and moisture-absorbent layer 1 are of the samewidth and are joined to one another over their length by means ofhotmelt dots. The assembly of 1 and 2 is joined to layer 3, the width ofwhich is greater. Layer 3 is fixed onto the top edge of layer 2 by beingfolded over it.

In FIG. 7, the wider top layer 2 is joined to the narrowermoisture-absorbent layer 1. The moisture-impermeable layer 3 is joinedto the assembly of 1 and 2 and folded over onto the moisture-permeabletop layer 2 which projects beyond layer 1.

FIG. 8 shows an embodiment with handles. In this case, after thethree-layer assembly has been produced, stamping is used to form anassembly in which both sides of the underpad have been stamped into theshape of two semi-ovals 25 in the longitudinal direction. Openings 26which form handles are punched into these shapes.

In the embodiment shown in FIG. 9, the top layer 2 is on both sides 30to 40 cm wider than the absorbent layer 1 and the moisture-impermeablebottom layer 3. This embodiment facilitates fixing the underpad in placeby tucking it in.

In the embodiment shown in FIG. 10, the moisture-impermeable bottomlayer 3 is 30 to 40 cm wider than the top layer 2 and the absorbentlayer 1. This too facilitates fixing of the underpad by tucking it in.

FIG. 11 shows a preferred design of the screen-printing stencil forapplying a pattern of adhesive composition in the interface between twolayers which bear against one another in the ready-to-use state of awashable multilayer material. Depending on the design aspects, thepattern can be applied to one layer or the other and can function in theinterface when the layers are being joined together.

The figure shows a pattern composed of sets of circles, with the centreof each of the three sets lying at a corner of an equilateral triangle.

In the case of a rotary screen-printing stencil of type CP52-18%-200 μm,pattern part 1 has an external diameter of 22 mm and is open, part 2 hasan external diameter of 18 mm and is closed, part 3 has an externaldiameter of 13 mm and is open, part 4 has an external diameter of 9 mmand is closed and pattern part 5 has an external diameter of 4 mm and isopen. In this context, the term open means that the holes in the stencilare not covered and allow an adhesive composition to pass through. Apattern part of this type, depending on the form of printing, is acompletely continuous pattern part or a pattern part composed of dots.In the latter case, the dimensions of the dots correspond to thedimensions of the holes in the stencil.

As has been indicated above, the term washable underpad encompasses notonly the underpad per se, but also the material which can be used forother purposes.

The Applicant has successfully used the material in:

-   sanitary towels-   incontinence products for patients who are not bedridden-   anti-leak material at stomas-   bibs for babies and adults-   medical dressings-   operating chamber covering cloths and textiles (sterilizable)-   washable diapers-   saddlecloths for horses-   dog/cat mats-   recreational beach mats-   car seat mats (to combat perspiration)-   disinfecting running mats (optionally sterilizable)-   washable sterilizable plasters-   dressing material-   sleeping mats-   filter material-   breast compressors-   incontinence material for men-   doormats-   liquid-absorbent mats.

1. A multilayer washable material which comprises: a moisture-permeabletop layer material (2) being substantially hydrophobic, amoisture-impermeable bottom layer material (3), and at least one layerof a textile material used as a moisture-absorption element (1)positioned between the top layer and the bottom layer; the layers beingjoined to one another by means of an adhesive composition, wherein aninterfacial region between each pair of layers bearing against oneanother exists; wherein in the interfacial region between each pair oflayers bearing against one another there is an adhesive composition inthe form of a pattern which is sufficiently dense to prevent wrinkling,and which is sufficiently open to prevent the material from becominginflexible; wherein the pattern in which the adhesive composition ispresent is selected from: a) a dot lining pattern, b) separatelypositioned pattern parts which are separated by regions where there isno adhesive composition, c) a number of pattern parts (4, 22) which areidentical in shape and one or more pattern parts (21) of a differentshape, wherein the different pattern shape is a border, the externaldimensions of which correspond to the dimensions of a use product, whichit is desired to form from the multilayer material by dividing up thelatter, d) the patterns described under b) and/or c), with one or morepattern parts being formed from a dot lining pattern, e) a dot liningpattern as described under a) in which there are parts without any dots,and combinations of the patterns described under a) to e); wherein themultilayer material is a washable underpad; wherein themoisture-permeable top layer is made of a fraying-free fabric; whereinoptionally no finishing of the multilayer material, as such and/or of asmaller part obtained therefrom, is carried out; and wherein a quantityof applied adhesive composition is from 6 to 40 g/m².
 2. The multilayermaterial according to claim 1, wherein the adhesive composition isselected from solidified, nonreactive thermoplastic material and a fullymoisture-cured reactive hotmelt adhesive.
 3. The multilayer materialaccording to claim 2, wherein the adhesive composition is a fullymoisture-cured reactive polyurethane hotmelt adhesive.
 4. The multilayermaterial according to claim 1, wherein the multilayer material comprisesone or more additional layers of material selected from an anti-allergylayer, a resilient foam layer, a dispersion layer, an anti-bedsore layerand an anti-odour layer, which are bonded to the moisture-absorptionelement (1) and the top layer material (2) or the bottom layer material(3).
 5. The multilayer material according to claim 1, wherein themoisture-permeable top layer material comprises a knitted polyestermaterial comprising approximately 85% polyester fibers, and wherein themoisture-impermeable bottom layer material comprises PVC.
 6. Themultilayer material according to claim 5, wherein the quantity ofapplied adhesive composition is approximately 15 g/m².
 7. A method forproducing a multilayer washable material which comprises amoisture-permeable top layer material (2) being substantiallyhydrophobic, a moisture-impermeable bottom layer material (3) and atleast one layer of a textile material used as a moisture-absorptionelement (1) positioned between them, wherein the top layer material (2),the bottom layer material (3) and the moisture-absorption element (1)are provided and are joined to one another using an adhesivecomposition, wherein an interfacial region between each pair of layersbearing against one another is formed, wherein an adhesive compositionis applied in a quantity of from 6 to 40 g/m² in the form of a patternwhich prevents wrinkling and which is sufficiently open to prevent thematerial from becoming inflexible both in the interfacial region whichis to be formed between top layer material (2) and themoisture-absorption element (1) and in the interfacial region which isto be formed between bottom layer material (3) and themoisture-absorption element (1), and the layers are brought to bearagainst one another and are joined to one another as the adhesivecomposition sets, and wherein the multilayer material is a washableunderpad, the pattern in which the adhesive composition is applied isselected from: a) a dot lining pattern, b) separately positioned patternparts which are separated by regions where there is no adhesivecomposition, c) a number of pattern parts (4, 22) which are identical inshape and one or more pattern parts (21) of a different shape, whereinthe different pattern shape is a border, the external dimensions ofwhich correspond to the dimensions of a use product, which it is desiredto form from the multilayer material by dividing up the latter, d) thepatterns described under b and/or c), with one or more pattern partsbeing formed from a dot lining pattern, e) a dot lining pattern asdescribed under a) in which there are parts without any dots, andcombinations of the patterns described under a) to e).
 8. The methodaccording to claim 7, wherein the adhesive composition is selected froma nonreactive thermoplastic material which is solid under ambientconditions and a moisture-curable plastic material, and it is applied inthe form of a melt at a temperature which is higher than the meltingpoint of the plastic material used.
 9. The method according to claim 8,wherein a moisture-curable plastic material is applied to the top layermaterial (2) and the bottom layer material (3).
 10. The method accordingto claim 9, wherein a molten moisture-curable plastic material isapplied with the aid of screen printing, with at least the stencil usedbeing heated to above the melting point of the moisture-curable plasticmaterial used.
 11. The method according to claim 10, wherein the screenprinting used is rotary screen printing using one or more seamlesscylindrical metal stencils (5, 6).
 12. The method according to claim 8,wherein the moisture-curable plastic material used is a plastic materialselected from a reactive polyurethane hotmelt adhesive and a reactivepolyalkene hotmelt adhesive.
 13. The method according to claim 12,wherein a reactive polyurethane hotmelt adhesive is used.
 14. The methodaccording to claim 7, wherein to form a multilayer material in the formof a washable underpad with the aid of rotary screen printing, a patternof a moisture-curable plastic material is applied to themoisture-permeable top layer material (2) and to themoisture-impermeable bottom layer material (3), and the materials whichhave been coated in this way are combined with the moisture-absorptionelement (1) in such a manner that the sides of the top layer material(2) and the bottom layer material (3) which comprise moisture-curableplastic material bear against the two surfaces of themoisture-absorption element (1), and curing of the moisture-curableplastic material bonds together the top layer material (2), bottom layermaterial (3) and the moisture-absorption element.
 15. The methodaccording to claim 14, wherein the top layer material (2) and the bottomlayer material (3) are in web form, and moisture-curable plasticmaterial (7, 9) is applied to both materials simultaneously with the aidof two rotary screen-printing stencils (5, 6), and the top layer andbottom layer materials which have been coated in this way are brought tobear against a moisture-absorption element in web form, after whichmoisture-curing of the moisture-curable plastic material bonds togetherthe top layer material (2), bottom layer material (3), andmoisture-absorption element (1).
 16. The method according to claim 15,wherein it is carried out continuously, and after an assembly of toplayer material (2), bottom layer material (3) and moisture-absorptionelement (1) in web form has been formed, the web is divided intoseparate, washable underpads by cutting, and these underpads are usedwith the need for separate edge finishing being obviated.
 17. The methodaccording to claim 14, wherein one or more additional layers of materialselected from an anti-allergy layer, a resilient foam layer, adispersion layer, a bedsore-inhibiting layer and an anti-odour layer areapplied and these layers are bonded to the absorption element (1) andthe top layer material (2) or the bottom layer material (3).
 18. Themethod according to claim 7, wherein to fully cure the moisture-curableplastic, moisture is supplied in an amount sufficient to enable themoisture-curable plastic on the top layer material (2) and bottom layermaterial (3) to cure fully.
 19. The method according to claim 14,wherein the pattern on the top layer material (2) and the bottom layermaterial (3) extends over the entire surface thereof and comprises dots,or the pattern parts (4, 21, 22) are composed of dots.
 20. The methodaccording to claim 7, wherein the moisture-permeable top layer materialcomprises a knitted polyester material comprising approximately 85%polyester fibers, and wherein the moisture-impermeable bottom layermaterial comprises PVC.
 21. The method according to claim 20, whereinthe quantity of applied adhesive composition is approximately 15 g/m².